1. Field of the Invention
This invention relates in general to a magnetic disc cartridge in which a disc-shaped, extremely thin magnetic recording medium, namely, a magnetic disc sheet, is rotatably supported. More particularly, the invention relates to a magnetic disc cartridge in which a liner is in sliding contact with the magnetic disc sheet to protect and clean the sheet.
2. Background Art
In general, writing magnetic recording data into a magnetic disc sheet or reading the data out of it is carried out with a writing or reading head which is moved radially with respect to the sheet which is being rotated. Therefore, dust, contaminating material, or particles on the surface of the sheet may cause failures in reading or writing of data, i.e., dropouts. This difficulty is serious because magnetic disc cartridges are used mainly as digital data memories in computers or the like and a single data error may be unacceptable.
Accordingly, in some of the conventional magnetic disc cartridges, the cases are made of relatively flexible pressed paper or synthetic resin, or hardened synthetic resin, and have openings provided with dust shutters. In each of these cases, a liner made of unwoven cloth or the like is provided on the inner wall, to protect the magnetic disc sheet and to remove dust, etc. from the surface of the sheet. In some of the conventional magnetic disc cartridges, a spacer of synthetic resin or the like is provided between the liner and the inner wall of the case. The spacer brings the liner into elastic contact with the surface of the sheet, to improve the cleaning effect of the liner.
As is apparent from the above description, various protecting means such as means for preventing charging and dustproofing means utilizing a dust absorbing or collecting action are provided. However, these means still produce unsatisfactory results. Furthermore, after the magnetic disc cartridge is used for a long period, fibers become detached from the liner and drop onto the magnetic disc sheet. Also, external dust particles gradually accumulate on the magnetic disc sheet, thus causing frequent dropouts.